New Graphics Card locks access to computer

Long story short, in 2013, I bought a pre-built computer, and put a GTX 770 in it. At the time, I didn't know enough about computers to build my own, really, so I had Geek Squad do it, since I was given warranty for free. Now, I plan on installing an older graphics card into it, and giving it to my uncle, and actually building my own.

I installed an older graphics card, and replaced my 600W power supply with my old one. I turn the computer on, only to hear 6 beeps. I looked up what this meant online, and basically the computer locks access to aftermarket GPUs. I put the 770 back in, and disabled Secure Boot, but I was still getting the same problem. I've exhausted what I know about PCs, and my warranty is expired, so I can't take it to Geek Squad.

Any suggestions as to what I could be doing wrong? Thanks.

Put the other power supply back in.

Yeah, it's generally a good idea to swap one component at a time to make sure that you have as few variables as possible.

Which one, the 600W or the 460W? I'm not sure that will help, considering when I take out the graphics card I just purchased, there's no beeping.

I swapped the RAM around, Power supply, nothing. But I took out the graphics card completely, no beeping, then put it back in, and it started beeping.

Try putting the build back to it's original state. See if that works. If yes, try swapping ONLY the GPU. Let us know what happens then.

Yep

Swapped only the GPU. I had another GPU laying around, so I put that in, still got beeping. I took out the gpu altogether, and the beeping ceased.

Try removing the CMOS battery for a few minutes and see if the fresh BIOS settings will help.

NEVER use Geek Squad. Lesson learned.

CMOS might do it but it sounds like a OS thing. I have not heard of a BIOS locking down the hardware like that. I think some versions of Windows flip out if the hardware has changed enough.

I mean I wouldn't criticize geek squad, they got the job done, but it was just inconvenient timing for me.

As for the CMOS thing, I'm gonna try that before I go to sleep, but I don't know if that's the problem. I think my real mistake was buying a pre-built instead of building it myself, but I was too young to be able to buy stuff on my own then, and I didn't know much about PCs, so I kinda got screwed.

Could you try putting your 770 back in?

Yeah. The way that I even got legacy boot turned off was putting the 770 and the 600w power supply back in the rig and going to the bios.

Yeah, just trying to rule out all the easy solutions before we get to the more drastic measures.

Speaking of which, if you have a windows install disk, try popping that in and running repair mode or whatever it's called.

hmm. true. But I wouldnt call reinstalling Windows a "drastic" measure. I would call it an everyday thing at the IT office.

Yeah, but it's a colossal pain in the ass if you don't have backup EXE's for all the shit that you use (and let's face it, most people don't)

OP said that they were giving the computer to someone else, so I'm sure a fresh install of the OS is what they had planned anyways, if not, it's a good idea.

OP: Does the computer actually POST and attempt to boot with the graphics card installed? Usually those beep codes means the computer isn't able to even POST.

It works with the graphics card I originally had, but beeps when I put in the other graphics card I just got.

That much I understand, but I'm trying to get a clearer definition on what is actually happening with the other graphics card installed. Does the computer power on, give you the beeps but still POST? Do you see anything on the screen? Are you able to access the BIOS with the graphics card installed?

Also, what's the make and model of the computer? Did you try switching the BIOS from UEFI to Legacy (if applicable)?

Can you try using the older Graphics card in a different computer? To make sure it's still working.

Also, what is the older Graphics Card?